Such dialogs can be unexpected and confusing, as reconnection can happen
automatically, and not in a response to a user action.
Implement this by adding a new "reconnect" option and add is_option_on()
helper to connection_parameters to facilitate using it.
This function can be used to check if the connection to the server is
still available (and then, perhaps, call reconnect(), if it isn't).
Implement it for all backends using native API (except for SQLite for
which it always returns true).
Vadim Zeitlin